Optical element having a toric surface

ABSTRACT

An image forming system is described that includes a light source that provides a light beam and an anamorphic refractive optical element. A first outer surface of the anamorphic element faces the light source and includes a toric surface. The light beam is incident upon the first outer face and then an incident surface of the anamorphic element. The anamorphic element directs the light beam to an image forming device. An illumination system is also described where an anamorphic element includes a toric surface and a facet surface.

This application is a continuation of U.S. application Ser. No.12/276,818, filed on Nov. 24, 2008 now U.S. Pat. No. 8,136,947,published as U.S. Patent Application Publication No. 2009/0141503, nowallowed, which claims the benefit of U.S. Provisional patent applicationSer. No. 60/991,553, filed Nov. 30, 2007, the contents of which ishereby incorporated by reference in its entirety.

BACKGROUND

Optical projectors are used to project images onto surfaces for viewingby groups of people. Optical projectors include optical projectorsubsystems that include lenses, filters, polarizers, light sources,image forming devices and the like. Fixed front and rear electronicprojectors are known for use in education, home theaters, and businessmeetings. Known light sources include black body lamps, gas dischargelamps, and solid state sources such as lasers, light emitting diodes(LED's) and organic light emitting diodes (OLED's). Head mounteddisplays are known for individual use. For mobile applications, there isa desire to miniaturize the volume and thickness of optical projectors,and make them power efficient while maintaining low power consumption,low cost and high image quality. However, the large dimensions and highpower consumption of existing optical projection subsystems limitefforts to create a truly portable projector. Optical projectionsubsystems and methods of making subsystems are needed that provide bothminiaturization and efficiency to project good quality images in a costeffective manner.

SUMMARY

In one embodiment, an image forming system includes a light source thatprovides a light beam and an anamorphic refractive optical element. Theanamorphic element includes a first outer surface for facing the lightsource and an incident surface. The first outer surface includes a toricsurface. The anamorphic element is configured so that the light beam isincident on the first outer surface and then the incident surface. Thesystem further includes an image forming device, where the anamorphicoptical element directs the light beam to the image forming device.

In another embodiment, an illumination system includes a light sourcethat provides a light beam and an anamorphic refractive optical element.The anamorphic element includes a first outer surface for facing thelight source. The first outer surface includes a toric surface and afirst facet cut surface.

In yet another embodiment, a method of making an anamorphic component ofan illumination system includes the steps of providing a portion of lensmaterial having an edge surface, rotating the portion of lens materialabout a first rotation axis, and while the portion is rotating, cuttinginto the edge surface to form a toric surface. The method furtherincludes the step of cutting a first facet cut surface in the toricsurface.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, is not intended todescribe each disclosed embodiment or every implementation of theclaimed subject matter, and is not intended to be used as an aid indetermining the scope of the claimed subject matter. Many other noveladvantages, features, and relationships will become apparent as thisdescription proceeds. The figures and the description that follow moreparticularly exemplify illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed subject matter will be further explained with reference tothe attached figures, wherein like structure or system elements arereferred to by like reference numerals throughout the several views.

FIG. 1 is a top view of one embodiment of a mobile projection systemincluding a faceted optical element having a toric surface on itsentrance face.

FIG. 2 is a top view of the optical element of FIG. 1.

FIG. 3 is a perspective view of the optical element of FIG. 2.

FIG. 4 is a side view of one embodiment of an optical element having atoric surface.

FIG. 5 is a perspective view of an optical element having a toricsurface, which is an intermediate form during the manufacture of theoptical element of FIG. 2.

FIG. 6 is a cross-sectional view of the optical element of FIG. 5, alongline 6-6 in FIG. 5.

FIG. 7 is a perspective view of an optical element having a toricsurface with cylinder facet cuts, which is another intermediate formduring the manufacture of the optical element of FIG. 2.

FIG. 8 is another perspective view of the element of FIG. 7.

FIG. 9 is a schematic drawing showing a 2½ axis lathe that is used tomanufacture a lens having a toric surface with added cylindrical facetsin one embodiment of the invention.

FIG. 10 is a top view of one embodiment of a mobile projection systemhaving a digital micro-mirror imager and having an optical element witha toric surface.

FIG. 11 is a top view of one embodiment of a mobile projection systemhaving a transmissive polarized imager and having an optical elementwith a toric surface.

FIG. 12 is a top view of a mobile projection system including a dualcylinder lens prior to the entrance face of a polarizing beam splitter.

FIG. 13 is a top view of a mobile projection system including a cylinderlens as an entrance face for a polarizing beam splitter.

FIG. 14 is a top view of a projection system including three colorchannels.

While the above-identified figures set forth one or more embodiments ofthe disclosed subject matter, other embodiments are also contemplated,as noted in the disclosure. In all cases, this disclosure presents thedisclosed subject matter by way of representation and not limitation. Itshould be understood that numerous other modifications and embodimentscan be devised by those skilled in the art which fall within the scopeand spirit of the principles of this disclosure.

DETAILED DESCRIPTION

The present invention is applicable in the context of image formingsystems. One example of a context where the present invention isparticularly applicable is projection systems, especially mobileprojections systems.

There are many different configurations for projection systems, butseveral have in common that they direct a light beam from a light sourceto a reflective or transmissive image forming device which includes animage forming panel. These different image forming devices commonly usean anamorphic optical element to transform a light beam from a lightsource with a first aspect ratio to a light beam with a second aspectratio that matches an image forming panel. Typically, the light sourcehas a square aspect ratio of 1:1. In various examples, the image formingpanel has a rectangular aspect ratio of 16:9 or 4:3, or otherrectangular aspect ratios.

The anamorphic element typically compresses the light beam in onedirection in order to achieve the altered aspect ratio. An exemplaryanamorphic refractive optical element that serves this purpose isillustrated in FIG. 1 in the context of an image forming system 100. Therefractive optical element 110 includes a first outer surface 112 thatfaces a light source 114. The outer surface 112 includes a toric surfaceportion 118. It has been discovered that the toric surface is especiallyuseful for directing light from the light source toward the center ofthe element. Particularly, light that impacts the top and bottomportions of the first outer surface 112, as oriented in FIG. 1, will bedirected toward the center.

A toric surface is a surface of a torus, where a torus is a shape formedby the revolution of a curve or line about an exterior line lying in thesame plane as the line. One common torus is the donut-shape generated bythe revolution of a circle. The term torus, however, refers to any shapegenerated by the revolution of a conic. A conic is a curve or anon-straight line, formed by the intersection of a plane with a rightcircular cone, including an ellipse, a parabola, and a hyperbola. As theterms toric and toroid are used in this application, the curve used togenerate the torus can be described by polynomials, as is the case inthe example shown in the FIGS. Additional aspects of the first outersurface will be further described herein, after a description ofprojector systems in which the anamorphic element is used.

Refractive optical elements for providing a rectangular aspect ratio areused in many different types of projector systems. One example of areflective image forming device is an image panel using liquid crystalson silicon (LCoS). Light reflects from the LCoS image panel to form animage beam. Another example of a reflective image panel is a digitalmicromirror device (DMD) that is made up of a matrix of microscopicmirrors, where each mirror represents one or more pixels in theprojected image. The mirrors can be moved quickly from an on-position inwhich they reflect light to an off-position where they direct light toan absorbing element. Some transmissive systems use light gates thatopen or close to allow light to pass or to block light for individualpixels. Another example of a transmissive system is a high-temperaturepolysilicon liquid crystal device (HTPS-LCD) imager.

FIG. 1 illustrates the anamorphic refractive optical element 110 in thecontext of an example of a reflective projection system 100, such as asystem with an LCoS panel. This system will be described initially toprovide context for understanding the operation of the refractiveoptical element 110. The light source 114 provides a light beam 122 andincludes a solid state light emitter 126, a collection lens 128 and acollimator 130. The solid state light emitter 126 receives electricalpower 131 and thermally couples to a heat sink, which is not shown. Inone example, the light beam 122 comprises incoherent light. In anotherexample, the solid state light emitter 126 comprises one or more lightemitting diodes (LED's). In one example, the collection lens 128 is ahyper-hemispheric ball lens as taught in U.S. Patent Publication No.2007/0152231, the contents of which are hereby incorporated by referencein its entirety for any purpose.

In this example, the collimator 130 includes a focusing unitincorporating a first Fresnel lens having a first non-faceted side forreceiving a first non-collimated beam and a first faceted side foremitting the collimated beam.

The collimator 130 directs the light beam 122 to the refractive element110. The first outer surface 112 of the refractive element 110 faces thelight source. In the example of FIG. 1, the incident surface 132includes a polarizing filter 134 to form a polarized beam 136 having afirst polarized component which is directed toward an image panel 140.The anamorphic element 110 acts as a polarizing beam splitter (PBS) inthis example. In this configuration, the refractive element 110 is amultifunction optical component that functions as a polarizing elementas well as a lens, and functions as an anamorphic element. Thiscombination of functions prevents losses that would otherwise occur atair interfaces between separate components that provide these functions.

In various embodiments, the polarizing filter is an absorptivepolarizer, or a reflective polarizer such as a wire grid polarizer,birefringent polarizer or a thin film polarizer. In the arrangementillustrated in FIG. 1, polarizing filter 134 is a reflective polarizinglayer that directs a polarized beam 136 including primarily light of afirst polarization toward the image panel 140. A second polarizedcomponent passes through the polarizing filter 134. The polarized beam136 exits the refractive element through a second outer surface 144. Inone example, the second outer surface 144 has a non-zero lens power andis a curved lens surface, such as a convex surface. The second outersurface is an aspheric convex lens in the example of FIG. 1.

The image forming panel 140 receives image data and electrical powerfrom an electrical input bus 146. The polarized beam 136 is incidentupon the panel 140 which reflects light according to the image data. Amodified beam 142 is reflected from the panel 140 with polarizationstates that are modified relative to the polarization of the polarizedbeam 136 on a pixel-by-pixel basis according to the image data. Forpixels where the image is bright, the polarization state is modified,while for areas of the panel where the image is dark, the polarizationstate is not modified. The image beam 150 is composed of thepolarization components of modified beam 142 that pass through therefractive element 110 and through the polarizing filter 134.

The refractive element 110 is positioned immediately adjacent to a lenselement 154, having a first outer surface 156. In the example of FIG. 1,there is no air gap between the refractive element 110 and the lenselement 154. The image beam 150 passes through the lens element 154 to aprojection lens assembly 160. The projection lens assembly 160 providesan image projection beam 162 suitable for viewing. A commonly owned,co-pending patent application titled “Optical Projection System”, havingapplication Ser. No. 11/831,307, filed Jul. 31, 2007 provides additionaldetails about many aspects of exemplary projection systems in which therefractive element having a toric surface could be utilized. Thisapplication is hereby incorporated herein by reference in its entiretyfor any purpose.

In some embodiments, color is imparted to the projection light beamusing color sequencing such as by the action of a color wheel.Alternatively, three image panels can be used that are each illuminatedwith a primary color. Alternatively, color filters can be incorporatedinto the picture elements of image forming panel 140.

The first outer surface 112 will now be described in further detail.FIG. 2 is a side view and FIG. 3 is a perspective view of the refractiveelement 110 having a toric surface portion 118. Compared to having acylindrical surface shape for the first outer surface, the toric surfaceprovides additional mixing of light and a more efficient system. If apure cylindrical surface is provided, the light spreads out farther inthe vertical direction as oriented in FIG. 1. The toric surface portion118 is more effective at directing light from the top and bottomportions of the first outer surface 112, as oriented in FIG. 1, towardthe center of the incident surface 132.

Now referring to FIGS. 2-3, the first outer surface 112 includes a toricsurface portion 118 framed by facet cut surfaces 200, 210, 300 and 310.In alternative embodiments, the first outer surface is provided withone, two, three, five, six or other numbers of facet cut surfaces. Inone embodiment, one or more of the facet cut surfaces have cylindricalsurfaces. In one embodiment, the radius of one cylindrical facet cutsurface is different than at least one other cylindrical facet cutsurface. In the embodiment of FIG. 3, a first facet cut surface has twoportions: The first top facet cut surface portion 200 and the secondbottom facet cut surface portion 210 are cylindrical surfaces having thesame radius. A second facet cut surface also has two portions: The firstleft facet cut surface portion 300 and the second right facet cutsurface portion 310 are also both cylindrical surfaces having the sameradius as each other, but different from the radius of the first andsecond facet cut surface. FIG. 4 is a bottom view of the refractiveelement 110, where an edge of the second bottom cylindrical facet cutsurface portion 210 is visible. It is understood that the orientationreferences in the application, such as top, bottom, left and right,refer to the orientation as shown in the FIG. that is being discussed,and that these orientations are not required or even accurate when thesystems are in use.

FIGS. 5-8 are views of the refractive element 110 at different stages ofits formation. More detail will be provided about an exemplary firstouter surface 112 by describing an exemplary method for forming thesurface. In one exemplary method, a portion of element or lens materialis initially provided. The material portion is shaped while spinning inthis exemplary formation method, preferably using a lathe. In oneembodiment, the material of the refractive element is a plastic resinmaterial. U.S. Published Patent Application 2007/0030456 providesadditional detail regarding the materials and formation methods that canbe used for the anamorphic refractive element 110, and is herebyincorporated by reference in its entirety for any purpose. The materialportion is provided in a disk shape in one embodiment and is rotatedabout the axis of the disk by the lathe. Alternatively, another shape ofmaterial portion is used and is provided along with a fixture forrotating the material portion about an axis. Next, the material portionis rotated about a first axis. While the portion is rotating, a cut ismade into an edge surface to form a toric surface. In variousembodiments, the distance from the axis of rotation to the materialportion edge is greater than 20 mm, greater than 30 mm, less than 40 mm,less than 35 mm, 32 mm, or 32.25 mm.

The resulting cut toric surface 500 in a material portion 502 is shownin a perspective view in FIG. 5 and in cross-section in FIG. 6. Flatsurfaces 510 and 512 are used to secure the material portion 502 in aholder. The toric surface 500 of this embodiment is formed by rotationof a line or curve described by a polynomial equation.

The cross-section of FIG. 6 shows the curve or profile 600 used togenerate the toric surface 500. The profile is described by:

$z = {\frac{{cy}^{2}}{1 + \left\lbrack {1 - {\left( {1 + k} \right)c^{2}y^{2}}} \right\rbrack^{1/2}} + {Dy}^{4} + {Ey}^{6} + {Fy}^{8} + {Gy}^{10} + {Hy}^{12} + {{Iy}^{14}\mspace{14mu}\ldots}}$Where the y-axis and z-axis are shown in FIG. 6, the values of the z andy are expressed in millimeters, and the other variables in the equationhave the following values:

c k D E F G H I −11 mm. 0 −3.00 × 1.45 × −4.00 × 2.00 × 0 0 10⁻⁴ 10⁻⁴10⁻⁷ 10⁻⁸This equation is a polynomial equation as that term is commonly used inoptical design. The variable c is the radius of curvature in the y-zplane of the center portion of the toric surface. In this example, c isa negative value correlating to a concave surface at the center portionof the profile. The variable k indicates what type of cross-section of acone is used to generate the primary shape of the toroid, where 0indicates a circle, 1 indicates a parabola and −1 indicates a hyperbola.In the example profile described by the equation above, the variable kis zero, indicating that the primary profile component is a circle. Theterms beyond the first term in the equation modify the circle in theexample above. The series can continue with higher power terms. For theexample shown in the FIGS., the series was truncated at the 10^(th)order term. The axis of revolution 602 of the torus is illustrated inFIG. 6 and is perpendicular to the plane of the image panel 140 shown inFIG. 1.

Once the toric surface 500 is generated, next, the first facet cutsurface 200 and second facet cut surface 210 are created. A facet is adistinct portion of a surface which is at an angle compared to adjacentsurfaces. The piece of material 502, shown in FIG. 5 is rotated about anaxis of rotation and a lathe is used to cut a cylindrical surface intothe toric surface 500. In some embodiments, only one cylindrical surfacefacet cut is made in the toric surface 500. In the embodiment of FIGS. 7and 8, a first facet cut surface is shown, which has portions 200 and210, so that a toric surface portion 720 lies between them. The firstfacet cut surface portions 200 and 210 have cylindrical surfaces. In oneembodiment, the axis of the cylinder is the same as for the toricsurface, axis 602. In various embodiments, the radius of the cylindricalsurface of the first and second cut facet surfaces is greater than 20mm, greater than 30 mm, less than 40 mm, less than 35 mm, 32 mm, or32.25 mm.

The facet cut surfaces 200, 210 provide additional light mixing effectsand more uniform illumination over the desired aspect ratio than withoutthe facet cut surfaces. The toric surface 500 of FIG. 5 without anyfacet cuts results in a light distribution that has some brighter bands.The toric surface 500 of FIGS. 5 and 6 includes first ridge 514 andsecond ridge 516, which in profile have bent line profiles 518 and 520.The ridges 514 and 516 cause the brighter bands to be present spacedfrom a midline of the incident surface 132. To break up those bands anddistribute light more uniformly, the first and second facet cuts 200 and210 are provided.

The next step is to take the material portion 702 of FIGS. 7 and 8 andmake an additional facet cut 300 and 310 as shown in FIG. 3. This secondfacet cut surface has portions 300 and 310 that further break up thelight distribution and result in a more uniform light distribution thanwithout this facet cut.

Regarding the formation method, if the first facet cuts 200 and 210 wereformed on a disk-shaped piece of material, then the wedge shape of therefractive element 110 is cut out of the disk to form a material portionshaped like material portion 702. The piece of material 702 from FIG. 7is rotated about an axis of rotation and a lathe is used to cut acylindrical surface into the toric surface 720 and first and secondfacet cuts 200 and 210. In the embodiment of FIG. 3, the second facetcut surfaces 300 and 310 are made, so that a remaining toric surfaceportion 118 lies between them. The second facet cut surfaces 300 and 310have cylindrical surfaces. In one embodiment, the radius of thecylindrical surface of the second cut surfaces is the same and is lessthan the radius of the cylindrical surface of the first facet cutsurfaces. In various embodiments, the radius of the cylindrical surfaceof the second facet cut surfaces is greater than 2 mm, greater than 8mm, less than 20 mm, less than 15 mm, 10 mm or 11 mm.

The refractive element 110 illustrated in FIG. 3 can be manufacturedusing a 2 axis lathe, and does not require a more complex lathe formanufacturing. FIG. 9 is a schematic drawing of an exemplary lathe 900that is used to manufacture the refractive element 110. In the lathe, aheadstock 902 causes a spindle 904 to spin. The work piece 906 to be cutis affixed to the spindle 904 so that the work piece 906 can be spunabout an axis of rotation during cutting. The work piece 906 is eitherattached to the spindle 904 or is attached using a fixture. One side ofthe fixture or work piece is provided with support by a tailstock 908.The tailstock can be moved toward and away from the work piece alongtrack 910, as indicated by arrows 912, to provide support to the workpiece 906. A cutting tool 914 is positioned along side the work piece ona tool rest 915. The cutting tool can be moved toward and away from thework piece, as well as moved side to side in relation to the work piece,as indicated by arrows 916. Lathe 900 is referred to as a 2-axis lathebecause the cutting tool can move along 2 axes, as indicated by arrows916. This type of lathe is also sometimes referred to as a 2½ axis or a3 axis lathe, where the ½ axis or third axis refers to the rotation ofthe work piece. More complex 5-axis lathes are configured so that thecutting tool is also capable of moving up and down with respect to theplane of FIG. 9 and capable of tilting.

When cutting the toric surface 500 shown in FIG. 5, the cutting toolmoves along the radial edge of a material disk, or along a cylindricalsurface of a portion of material held in a fixture, to impart the shapeof the toric surface. The surface of the material or work piece thatfaces the cutting tool initially is therefore cylindrical. For the toricsurface 500, the cutting tool starts at a first edge of the work piece522 where it is cutting into the material, moves away from the disk overthe ridge 514, and then into the material at the center of the edge tocut more deeply. Then the cutting tool moves away from the disk againover ridge 516, and then toward the disk as it approaches edge 526.

A molding process, such as injection molding, can be used to replicatethe anamorphic refractive element 110. A diamond turning process or aglass casting process may also be used. While the anamorphic refractiveoptical elements have been shown as integral with, for instance, apolarizing beamsplitter or a TIR prism, one of skill in the art willrecognize that the anamorphic refractive optical element may be formedseparately and aligned with a polarizing beamsplitter or TIR prism. Forinstance, an anamorphic refractive optical element may be adhered to aPBS or a TIR prism using an optical adhesive, or may be aligned with aPBS or a TIR prism with air between the anamorphic optical element andthe subsequent PBS or TIR prism.

FIG. 1 illustrates an anamorphic refractive element in a projectionsystem configuration commonly used with an LCoS panel as the imageforming panel. An anamorphic refractive element having a toric surfacecan be used in many other types of projection systems also. FIG. 10 is atop view of a projection system 1000 that uses a digital micro-mirrordevice (DMD) as its image panel 1040 and also has an anamorphic element1010, where a first outer surface 1012 has a toric surface portion 1018.Examples of suitable DMD panels include products commercially availablefrom Texas Instruments, Inc., (Plano, Tex.) under the trade designationDigital Light Processing (DLP). Many other configurations for DMDprojection systems are possible with an anamorphic toric element, andFIG. 10 provides just one such example. The system 1000 of FIG. 10includes a light source 1014, which directs light through a color wheel1019, and then through an integrator rod 1020. A fold mirror 1021directs a light beam 1022 toward a first outer surface 1012 of ananamorphic refractive element 1010.

The anamorphic refractive element 1010 transforms a light beam 1022 froma light source with a first aspect ratio to a light beam with a secondaspect ratio that matches the DMD image forming panel 1040. Typically,the light source has a square aspect ratio of 1:1, but it is alsopossible for the light source to have a different aspect ratio. Invarious examples, the image forming panel has a rectangular aspect ratioof 16:9 or 4:3, or other rectangular aspect ratios. The anamorphicelement 1010 operates in the same way as discussed above for theanamorphic element 110, and is capable of the various configurationsdiscussed above for the anamorphic element 110, including having firstand second facet cut surfaces, each having two portions, as shown inFIG. 3.

Referring again to FIG. 10, a light beam having the rectangular aspectratio is directed by a total internal reflection (TIR) prism 1042 toimpact the image forming panel 1040, where an array of tiny tiltingmirrors is present. The tilt of each mirror is independently controlledby the data loaded into a memory cell associated with each mirror, sothat the mirrors steer reflected light and spatially map a pixel ofvideo data onto a pixel on a projection screen. Light reflected by amirror in an ON state passes through a projection lens assembly 1060 andis projected onto a viewing surface to create a bright field. On theother hand, light reflected by a mirror in an OFF state misses theprojection lens assembly 1060, which results in a dark field. Instead ofusing a single DMD image panel 1040 and color sequencing by the actionof a color wheel, alternatively, three DMD image panels can be used thatare each illuminated with a primary color.

Another type of an image-forming device is a high temperaturepolysilicon liquid crystal device (HTPS-LCD). An HTPS-LCD also includesa liquid crystal layer, in which the alignment can be controlledincrementally (pixel-to-pixel), as determined by the data correspondingto a video signal. The liquid crystal layer is sandwiched between twoglass substrates that contain an array of transparent electrodes, thusbeing adapted for operation in transmission. At the corner of eachHTPS-LCD pixel, there is a microscopic thin film transistor. Non-HTPStransmissive liquid crystal devices also exist. FIG. 11 is a top view ofone embodiment of a projection system 1100 having a transmissive LCDimaging panel 1140 and having an anamorphic optical element 1110 with atoric surface 1118. Many other configurations for projection systemswith transmissive imaging panels are possible with an anamorphic toricelement, and FIG. 11 provides just one such example. The system 1100 ofFIG. 11 includes a light source 1114 that provides a light beam 1122 andincludes a solid state light emitter 1126, a collection lens 1128 and acollimator 1130. The solid state light emitter 1126 receives electricalpower 1131 and thermally couples to a heat sink, which is not shown. Inone example, the light beam 1122 comprises incoherent light. In anotherexample, the solid state light emitter 126 comprises one or more lightemitting diodes (LED's). In one example, the collection lens 128 is ahyper-hemispheric ball lens as taught in U.S. Patent Publication No.2007/0152231, the contents of which are hereby incorporated by referencein its entirety for any purpose. The light source 114 directs the lightbeam 1122 to a first outer surface 1112 of the anamorphic refractiveelement 1110.

The anamorphic refractive element 1110 transforms the light beam 1122from a light source with a first aspect ratio to a light beam with asecond aspect ratio that matches the image forming panel 1140.Typically, the light source has a square aspect ratio of 1:1. In variousexamples, the image forming panel has a rectangular aspect ratio of 16:9or 4:3, or other rectangular aspect ratios. The anamorphic element 1110operates in the same way as discussed above for the anamorphic element110, and is capable of the various configurations discussed above forthe anamorphic element 110, including having first and second facet cutsurfaces, each having two portions, as shown in FIG. 3. The second outersurface 1124 is any shape needed to provide the desired lightingconfiguration to the image panel 1140.

A polarizing filter 1132 causes light having a first polarized componentto be transmitted to the image panel 1140. The image forming panel 1140receives image data and electrical power from an electrical input bus1146. The polarized light is incident upon the panel 1140 and light istransmitted through the image panel according to the image data, andthen passes through a second polarizing filter 1134 acting as apolarization analyzer. An image beam 1150 is transmitted by the panel1140 and the polarizers 1132 and 1134, and then is provided to theprojection lens assembly 1160.

An illumination system 1170 is illustrated in FIG. 11, incorporating thelight source 1114 and the anamorphic element 1110, which can be used inmany different application environments where it is desired toilluminate a rectangular area uniformly. This is desirable in medicaland dental contexts, as well as many other situations. Such anillumination system may include other components depending on thespecific application.

Many alternatives exist for the configurations of the projection systemsand illumination systems described with respect to FIGS. 1, 10 and 11.For example, one illumination system has three separate light sources.Each separate light source emits a different primary color. This systemcould be used in combination with a color combiner element, such as across-dichroic combiner, such as known combiners composed ofright-angled prisms coated with dichroic coatings. In one example, eachlight beam from each separate color source is directed through ahyper-hemispheric ball lens, then through a Fresnel element, and theninto the color combiner. In one alternative, a color sequencer is usedso that the desired color is radiated from the color combiner. Inanother alternative, mixed, white light emerges from the color combiner,and then is directed to an anamorphic element, and then to an imagingpanel, with polarizers incorporated as needed for the particular imagingpanel used. A color filter is used in the light path or in the pictureelements of the image forming panel in this embodiment. Then the lightis directed through an anamorphic element, to an imaging panel, and toprojection optics, consistent with the arrangements shown in FIGS. 1, 10and 11 for the different types of imaging panels.

In another embodiment shown in FIG. 14, a three-channel projectionsystem 1400 includes three light emitters directing light to threedifferent reflective imaging panels, such as LCoS imaging panels. Redlight emitter 1402 is present in light source 1412, green light emitter1404 is present in light source 1414 and blue light source 1406 ispresent in light source 1416. The components of the light sources 1412,1414 and 1416 are similar to those discussed for light source 114 inFIG. 1. The output of each light source is directed to an anamorphicelement 1408, 1409 and 1410, which also acts as a polarizing beamsplitter, which in turn directs the light to image forming panels 1442,1444 and 1446. The operations and details of the anamorphic elements1408, 1409 and 1410 and image forming panels 1442, 1444 and 1446 aresimilar to those discussed with respect to FIG. 1. Image beams 1447,1448 and 1449 from the respective assemblies 1410, 1420 and 1430 aredirected toward a color combiner 1440, such as a cross-dichroiccombiner, such as known combiners composed of right-angled prisms coatedwith dichroic coatings. The combined image beam 1450 is then directed toa projection lens assembly 1460. The space shown in FIG. 14 betweenassemblies 1410, 1420 and 1430 and the color combiner 1440 is optionaland is typically not present. In an embodiment where the assemblies1410, 1420 and 1430 abut the color combiner 1440, a lens or opticalsurface is provided at the exit face of the color combiner 1440. It willbe appreciated that the three channel configuration of FIG. 14 usingreflective imaging panels could be adapted other types of imagingsystems, such as the digital micro-mirror imaging system of FIG. 10 andthe transmissive imaging system of FIG. 11.

EXAMPLES

FIGS. 12 and 13 illustrate two alternative designs for an anamorphicelement in a projection system, where the anamorphic elements in FIGS.12 and 13 do not have a toric surface. Various features of the systemsof FIGS. 1, 12 and 13 were tested empirically and simulated usingTracePro® optical modeling software available from Lambda ResearchCorporation of Littleton, Mass. Comparisons were made of differentcharacteristics of the three systems, as shown below in Table 1.

TABLE 1 Comparison of Configurations of FIGS. 1, 12, and 13 SimulatedMeasured Measured Efficiency Simulated Illumination Efficiency RIConfigu- at RI @ 95% Path at @ 90% ration LCoS Field Length Screen FieldFIG. 12 33.7%   34% 32.9 mm 6.56% 18.2% FIG. 13 28.1% 49.2% 34.3 mm 5.7%   35% FIG. 1 31.0% 48.2% 26.8 mm 6.75% 37.8%

Compared to the configurations of FIGS. 12 and 13, the illumination pathlength and overall volume of the configuration of FIG. 1 are decreased.Also, the configuration of FIG. 1 as built and measured achieves higherefficiency and better relative illumination (RI).

FIG. 12 is a top view of a mobile projection system 1200 including adual cylinder lenses that act as an anamorphic element prior to theentrance face of a polarizing beam splitter (PBS) 1227. The light source1214 includes an emitter 1226 that directs a light beam to cylinder lens1209, which in turn directs light to a second, crossed cylinder lens1208 having face 1211. The PBS 1227 includes a convex entrance face 1229and a reflective polarizing layer 1234 on an incident surface 1232. Thereflective polarizing layer 1234 directs the light toward the LCoS imagepanel 1240, which in turn directs the image beam back through the PBS1227 and through the projection lens assembly 1260.

FIG. 13 is a top view of a mobile projection system 1300 which issimilar to the system of FIG. 12, but instead of a dual cylinder lens1208, a cylinder lens 1308 is incorporated into the entrance face 1309of the PBS 1327.

The system of FIG. 1 that was tested empirically and by optical modelingincludes a solid state light emitter which is a white LED made with ablue InGaN die, part number C450-EZ1000-530000, plus a conformal yellowphosphor, produced by Cree, Inc. (4600 Silicon Drive, Durham, N.C.27703). The collection lens, and its coupling to the LED, is describedin US Patent Publication US 2007/0152231. The collimator is a Fresnellens having a non-faceted side for receiving the non-collimated beam anda faceted side for emitting the collimated beam. For the empiricallytested system, the anamorphic element 110 was made using a plasticmaterial and the first outer surface was shaped using a lathe. Thereflective polarizing film within the PBS is manufactured by 3M Company(St. Paul, Minn. 55144) under the trade designation “VIKUITI” advancedpolarizing films (APF). The image-forming device is an LCoS microdisplaywith internal red, green and blue color filters, part numberHX7007ATBFA, produced by Himax Display (2F, No. 26, Zih Lian Road, TreeValley Park, Sinshih, Tainan County 74445, Taiwan). This system has aresolution of 640 pixels by 480 pixels, and an aspect ratio of the imagepanel of 4:3.

Values of simulated efficiency at the LCoS panel and simulated relativeillumination (RI) at 95% Field, shown in the second and third columns ofTable 1, were determined using the TracePro® optical modeling software.The simulated efficiency at the LCoS imaging panel is a ratio of thelight received at the LCoS panel to the light output by the lightsource. The simulated relative illumination at 95% field is a ratio ofthe illumination taken at a first point compared to the illumination atthe center of the LCoS panel. If a line is drawn from the center to acorner of the LCoS panel, the first point is located at 95% of thedistance from the center toward the corner along that line. Thiscalculation was made for four points along lines drawn to each corner,and the results were averaged. A similar calculation method was used forthe measured relative illumination at 90% field. During the empiricalmeasurements, an all white image was projected on a screen surface. Theimage diagonal size was 23 inches. Measurements were taken with aMinolta CL-200 light meter.

Various modifications and alterations of this invention will be apparentto those skilled in the art without departing from the scope and spiritof this invention, and it should be understood that this invention isnot limited to the illustrative embodiments set forth herein. All U.S.patents, patent application publications, and other patent andnon-patent documents referred to herein are incorporated by reference,to the extent they are not inconsistent with the foregoing disclosure.

1. An image forming system comprising: a light source that provides alight beam; an anamorphic refractive optical element comprising a firstouter surface for facing the light source and an incident surface,wherein the first outer surface includes a toric surface, wherein therefractive optical element is configured so that the light beam isincident on the first outer surface and then the incident surface; and adigital micro-mirror imager; wherein the anamorphic element directs thelight beam to the digital micro-mirror imager.
 2. The system of claim 1wherein the toric surface is generated by revolution of a curvedescribed by a polynomial.
 3. The system of claim 1 wherein the firstouter surface further comprises a first facet cut surface.
 4. The systemof claim 3 wherein the first facet cut surface is a cylindrical surface.5. The system of claim 3 wherein the first outer surface furthercomprises a second facet cut surface.
 6. The system of claim 5 whereinthe first facet cut surface and second facet cut surface are cylindricalsurfaces.
 7. The system of claim 6 wherein the first facet cut surfacehas a first cylindrical diameter and the second facet cut surface has asecond cylindrical diameter different than the first cylindricaldiameter.
 8. The system of claim 1 wherein the first outer surfacecomprises a plurality of facets of differing optical power.
 9. Thesystem of claim 1 wherein a relative efficiency of the image formingsystem measured at a viewing surface is at least about 5% and a relativeillumination of image forming system at the viewing surface is at leastabout 30%.